1. Field of the Invention
The present invention relates to a method for adjusting color temperature in a PDP (Plasma Display Panel).
2. Description of the Related Art
In a picture receiver such as a cathode ray tube (CRT) or a PDP, several color temperatures can be adjusted within a temperature range of about 6000° C. to 12,000° C. so that the color temperature can be varied according to user's taste.
Such color temperatures of a display screen of the picture receiver can be adjusted variably by changing the level of each of RGB (red-green-blue) signals. Here, in the case of a picture receiver using the PDP, each of the RGB signals is subjected to level converting color temperature change before an analog input image signal is A/D (analog-to-digital) converted.
FIG. 4 shows an example of a picture receiver using the PDP as a display unit. The PDP is comprised of level adjustors 10A to 10C for changing the level of each of RGB signals in an input image signal a, A/D converters 11A to 11C for A/D converting the level of each of the RGB signals adjusted by the level adjustors 10A to 10C, a γ converting unit 12 for the luminance of each of the A/D converted RGB digital signals to be varied linearly, a luminous subfield selecting unit 13 for selecting a subfield corresponding to the luminance of each of the γ converted RGB digital signals, and a drive unit 14 for driving the PDP 15 according to the gradation frequency of the subfield selected by the luminous subfield selecting unit 13 to display the gradation of the PDP 15.
Here, when the user sets a desired color temperature, gains of the level adjustors 10A to 10C are reduced corresponding to the input level ratio of each of the RGB signals. This adjusts the level of each of the RGB signals from the level adjustors 10A to 10C. The level of each of the RGB signals adjusted by each of the level adjustors 10A to 10C is A/D converted by each of the A/D converters 11A to 11C, and sent to the γ converting unit 12 as each of the RGB digital signals. The γ converting unit 12 performs a γ conversion so that the luminance of the input digital signals can be linearly varied as described above, the luminous subfield selecting unit 13 selects the subfield corresponding to the level of each of the γ converted RGB signals, and the drive unit 14 drives the PDP 15 based upon the gradation frequency or the light emitting frequency selected by the luminous subfield selecting unit 13 and displays the gradation of the PDP 15.
The PDP device of the related art reduces the gain of the level adjustors 10A to 10C in response to the input level ratio of each of the RGB signals when the user sets a desired color temperature. Therefore, a problem takes place that the gradation of the PDP is lowered if the output level of each of the level adjustors 10A to 10C is lowered under the dynamic range of the A/D converter.